1. Field of the Invention
This invention relates generally to disk recorders, and more particularly to disk drive and read/write head-positioning apparatus in a magnetic disk recording machine.
2. Description of the Prior Art
Information storage in computers and similar devices is commonly performed by a magnetic disk recording unit wherein a plurality of stacked disks are rotated relative to a read/write head radially displaceable relative to the disk for selectively positioning the heads to a radial portion of the disk where information storage or retrieval is desired. It is important, however, that the recording heads ride on a film of air between the head and adjacent surface of an associated magnetic disk, since actual contact between the head and disk surface will severely damage the disk. So sensitive is the disk employed in such devices that there are recording units in actual use that are run continuously in order to avoid "freezing" of a recording head to a surface of a magnetic disk which the head contacts while the disk is stationary and resulting shattering of the heads when it is again set in motion.
U.S. Pat. No. 3,586,891, issued June 22, 1971, to R. A. Applequist, et al., discloses a magnetic recording disk drive wherein a linear positioning motor converts an electrical address signal directly into linear motion in order to position associated recording heads. A rack and pawl mechanism locks the recording heads at predetermined locations over the recording surfaces of associated recording disk, while a stationary cam cooperates with a loading ramp provided on an access arm of the head for directly loading and unloading the head as the access arm is moved radially of the magnetic disk. Such an approach tends to be relatively slow in reacting to instructions to change position because of the numerous mechanisms which must function at each movement of the head and due to the use of a carriage external of the linear motor for positioning the heads.
My prior U.S. Pat. No. 4,166,284, issued Aug. 28, 1979, discloses a read/write head-positioning apparatus for positioning one or more heads in a disk recorder and including a magnetic stator assembly having a co-axially, longitudinally-extending, annular coil-receiving cavity and a pair of longitudinally-extending, air bearing forming, passageways provided therein. An armature assembly including a pair of main bearing shafts is disposed to pass through the passageways and a member affixed to the shaft ends for carrying a cylindrical coil support adapted to carry a drive coil within the coil-receiving cavity and for receiving the head-carrying arms. A pump is coupled to the stator assembly to create an air bearing flow in the passageways around the main bearing shafts so the electro-magnetic interaction between the drive coil and the magnetic stator assembly can be used to position the recording heads with a minimum of frictional resistance. This arrangement, however, while very precise and fast-acting has encountered problems in manufacture due to the close control of tolerances required during assembly of the bearing shaft of the armature assembly into the armature itself and into the stator assembly.